1. Field of the Invention
The present invention relates generally to the sheet feeding apparatus which picks up a plurality of stacked sheet materials sheet by sheet and conveys a sheet material, more particularly to a sheet feeding apparatus including a pressure plate that brings the stacked sheet material into press-contact with a sheet feeding roller, and also to a recording apparatus including the sheet feeding apparatus, such as a printer, a copying machine, a printing apparatus, a facsimile, a scanner and so on.
2. Related Background Art
A typical system of a conventional sheet feeding apparatus including a pressure plate that brings a stacked sheet material into press-contact with a sheet feeding roller, is that the sheet feeding roller makes one rotation for, as in the invention disclosed in, e.g., Japanese Patent Application Laid-Open No. 2003-026349, a press-contacting/separating operation of the pressure plate with respect to the sheet feeding roller, a press-contacting/separating operation of a separation roller with respect to the sheet feeding roller via a torque limiter and a return lever operation of returning a leading end of the sheet material to a predetermined position. Namely, according to this system, the sheet feeding roller performs one rotation for one cyclic operations of respective members for feeding only one sheet material from a sheet stacking portion to a sheet lead-in roller provided on the side of a main body, which serves as an exit of an ASF (Auto Sheet Feeder). In a printer equipped with the thus-constructed sheet feeding apparatus, a main body unit of the printer is fed with the sheet material corresponding to a circumferential length of the sheet feeding roller from the sheet feeding apparatus.
In the prior art described above, however, if a necessary conveying length from the sheet stacking portion to the ASF exit elongates due to a structure of the main body unit attached with the ASF, it is required that the circumferential length of the sheet feeding roller be increased in order to complete the conveyance of the sheet material during one cyclic operations of the respective members. Namely, when the conveying length elongates, there is a necessity of increasing a diameter of the sheet feeding roller, thereby inducing rises both in size of the apparatus and in costs.
On the other hand, in the case of reducing the conveying length, the sheet feeding roller having a diameter corresponding to the conveying length must be prepared, and what is demanded is a construction capable of easily changing specifications without increasing the costs.